Differential heating system



Aug. 30, 1932;

c. A..DUNHAM DIFFERENTIAL HEATING SYSTEM Original Filed April 4, 1924 4 Sheets-Sheet l quill/Ill Aug. 30, 1932. c. A. DUNHAM DIFFERENTIAL HEATING SYSTEM Original Filed April 4, 1924 4 Sheets-Sheet 2 5% mi xxx Q 3 5i 5 n i Aug. 30, 1932. c. A. DUNHAM 1,374,937

DIFFERENTIAL HEATING SYSTEM Original Filed April 4, 1924 4 Sheets-Sheet 3 Aug. 30, 1932. DU M 1,874,937

DIFFERENTIAL HEATING SYSTEM 1 Original Filed April 4, 1924 4 Sheets-Sheet 4 Patented Aug. 30, 1932 UNITED STATES PATENT orncs CLAYTON A. :DUINHAM, OF GLENCOE, ILLINOIS, ASSIGNOR TO C. A. DUNHAM COMPANY, OF MARSHALLTOWN, IOWA, A CORPORATION OF IOWA DIFFERENTIAL HEATING SYSTEM Application filed Ap1'i14, 1924, Serial No. 704,142. Renewed November 9, 1927.

My invention relates to a steam heating system comprising separate supply and return mains and which is provided with mechanism for creating a low pressure in the return main; and the primary objects of the invention are: To provide a new and improved heating system in which the steam is circulated through the radiators, under ordinary conditions, at pressures much below atmospheric pressure; to provide a new and improved exhausting mechanism which will tend to create and maintain a relatively constant but regulatable pressure difi'erential as between the supply and return mains; to construct and arrange this mechanism so that it withdraws from the return pipe air and non-condensable gases only, and to provide for the return of the condensate to the boiler of the steam generator by gravity, or by means of a return trap or other device independent of the exhausting mechanism; to construct" the system so that the boiler and radiators may be maintained at pressures approximating the lowpressure of the return main so as to increase the volume of steam generated and its equal distribution to the radiators when the fire is low and to hasten the delivery of steam to the radiators when the apparatus is first started up; to provide means whereby this last mentioned efi'ect may be obtained wlthout drawing any appreciable amount of steam from the radiators into the return main; to provide means whereby the rate of generator of steam, that is, the fire of the generator may be controlled, so as to maintain the supply main, radiators and boiler at low pressures approximating that maintained in the return main or at any higher ressure as may be desired; to construct t e apparatus so that if the boiler pressure exceeds that at which condensate will return to the boiler by gravity a counterbalancing pressure will be built up in the return main which will permitsuch gravity return of condensate; and to construct the apparatus so that in case the exhaust mechanism fails to work the system will, nevertheless, be operated in the same manner as the ordinary gravity system using pressures above atmosphere.

The invention contemplates, more specifically, an electrically driven water pump and a jet exhauster arranged in a hurling circuit with the pump for creating the low pressure in the return main, and, assuming the use of this form of exhausting mechanism, the invention has for further objects: To provide an exhausting mechanism which will be small, compact and which will produce a relatively high vacuum with small consumption of current; to provide for supplying water to the hurling circuit from a source independent of the return main from the radiators, preferably, from the dri pipe or continuation of the supply main, w ich pipe is connected with the boiler, whereby condensate fromthe drip pipe and boiler water will be utilized for the hurling circuit and any excess of condensate returned by gravity to the boiler; to provide for the connection of the pump on its induction side to the drip pipe and on its eduction side to the atmosphere so that the force of the jet developed by the pump will be augmented by steam pressure in the boiler; to arrange the pump below the boiler water line to insure a constant supply of water to the hurling circuit; to arrange the exhausting pipe between the vacuum space of the jet exhauster and the return main so that air and non-condensable gases only will be drawn into the hurling circuit; to arrange the hurling circuit so that the water therein is used over and over again, fresh water being introduced only to replenish losses so that, because of the relatively low temperature of the hurling water the efficiency of the jet exhauster will be at a maximum; to provide the return main with a vertical leg extending above the boiler water line to such a distance that Water collecting therein overbalances any boiler pressure not in excess of that contemplated by the normal operation of the system; and to provide the exhausting mechanism and the other parts of the apparatus with certain check valves and float controlled valves whereby the system may be operated at or above atmospheric pressure if circumstances require.

The invention consists of the new and improved constructions, arrangements and devices to be hereinafter described and claimed for carrying out the above stated objects and such otheriincidcntal objects as will be mentioned in the following description of the preferred embodiments of the invention shown in the accompaning drawings.

It will be understood, however, that while the invention contemplates the use of all the devices shown in combination, and their combined use gives rise to the advantages to be hereinafter set forth, the invention is not to be considered as limited to the joint use of all of the novel features shown and described.

The invention is illustrated in certain preferred embodiments, in the accompanying drawings, wherein 1 Fig. 1 is a fragmentary View, in elevation, of one form of the invention.

Fig. 2 is a sectional view of the inlet valve on one of the radiators of the system.

Fig. 3 is a sectional plan view illustrating a portion of the pumping mechanism for maintaining pressure diflerential between the supply and return mains, this figure being taken on line 33 of Fig. 5.

Fig. 4 is a sectional elevation of the pumping mechanism.

F Fig. 5 is a sectional view on line 55 of Fig. 6 is a sectional view of the jet exhauster forming part of the pumping mecha-' nlsm.

Fig. 7 is a vertical sectional elevation of the device, hereinafter referred to as the air eliminator, for discharging air or other noncondensable gases from the return main.

Fig. 8 is a vertical sectional view of the differential pressure actuated device for controlling the pump motor.

Fig. 9 is a vertical sectional view of a modified form of radiator inlet valve.

Fig. 10 is a fragmentary elevation, partly diagrammatic, of the heatin system of my invention modified to provi e a return trap for introducing condensation from the return main into the boiler.

Referring first to Figs. 1 to 8 inclusive: A and A designate two of the radiators of the heating system, and B is the steam supply main opening out of the steam space of steam generator C and connected by supply pipes D with radiators A and A, respectively. E (Fig. 2) is a manually controlled valve between supply pipe D and each radiator, and F is a steam trap of any preferred construction at the outlet of the radiator, this trap being connected by a pipe 1 with the return main Gr, which latter is connected with the boiler of generator C below the water level therein and is provided with a check valve 2 ppening toward the boiler. At D and 1 are indicated supply and return pipes leading to another radiator, or group of radiators, on

another floor of the building. H is a drip pipe connecting the end of the steam main B with return main G between the check valve 2 and the boiler. I is a thermostatic trap arranged in a pipe 3 between the drip pipe H and the return main G for venting air from the drip pipe into the return main. J (Fig. 7) is an air eliminator connected by pipes 4 and 5 with the return main G and provided with an outwardly opening check valve 6. K is a thermostat, preferably, but not necessarily, employed for controlling the dampers 7 and 8 of the steam generator through the instrumentality of a damper operating motor 9, of common construction.

Condensation is returned to the boiler from return main G and drip pipe H by gravity. The air and non-condensable gases are withdrawn from the return main G through a pipe 10 by means of an exhausting apparatus consisting preferably of the following instrumentalities: L is a hurling water tank connected by pipe 11 to the drip pipe H. M is a centrifugal pump receiving water from tank L and forcing the same through a jet exhauster N to the suction space of which is connected the pipe 10, above referred to, leading from the return main G, this pipe being provided with a check valve 12 opening toward the jet exhauster. Water from the jet exhauster passes into an air separating tank 0 and thence back to the hurling water tank L, the air and gases being discharged to the atmosphere (under certain conditions) through an orifice 13 which is closed by a valve 14 operated by a float 15, the same float operating a valve 16 controlling the port 17 between the, air separator O and the hurling water tank L. The port 13 is provided with an outwardly opening check valve 18.

The pump M is preferably driven by an electric motor P, the controlling switch Q of which is governed by a differential pressure device R, the low pressure chamber of which is connected by pipe 19 with pipe 10 leading to the return main G and the high pressure side by means of pipe 20 with the hurling water circuit which is substantially at boiler pressure. S is a differential gauge or pres sure indicator connected by pipe 21 to pipe 10 (low pressure side of the apparatus) and by pipe 22'to pipe 11 (high pressure side of the apparatus).

From the above it will be observed that the induction side of the pump M is under boiler pressure; that the exhauster removes air (which term is intended to include non-condensable gases) from the return main of the heating system, drawing the same into the hurling water circuit to be discharged to the atmosphere by the air separator, without drawing into the hurling water circuit any water of condensation from the return main.

considerably above the water line of the boiler, designated a, a, so that water of condensation from the heating system will flow into the boiler of the generator by gravity of the hydrostatic head of water collecting in the vertical portion 24 of the return main above the boiler'water level so long, that is, as the boiler pressure is effectively less than the force exerted by such water column; that the return main is shut off from boiler pressure by check valve 2; that accumulation of water in the drip pipe to a height balancing boiler presure will'result in introduction of excess water in this pipe into the boiler; and finally, with the radiators filled with steam thermostatic valves F will be closed, opening only to void the radiators of air and water so that the exhausting apparatus cannot draw steam, inany substantial quantities, into the return main, while with insufiicient steam supply to fill the radiators the thermostatic valves F will be open so that the entire system will operate as a vacuum system, thereby effecting a lowering of the evaporation temperature of the boiler water.

' The operation of the system under various possible conditions will be summarized hereafter. Before doing this I will described in greater detail the constructions of the several instrumentalities generally referred to above.

Radiator valve E (Fig. 2). 25 is'a casing having an inlet port 26 communicating with supply pipe D and adapted to be closed by a valve 27 arranged on a structure 28 having a stem 29 provided on opposite sides with notches 30 for non-rotatable engagement with the nut 31 which has threaded engagement with an internally threaded sleeve 32 adapted to be rotated by a handle 33, the sleeve and handle being supported on the bonnet 34 of the valve casing. The stem 29 is non-circular in cross section and extends through an opening of similar shape in a guide plate 35 which is interposed between the upper edge of the casing and the bonnet.

Consequently, whenv the handle 33 is turned nut 31 is forced downwardly so as to seat the valve 27 over port 26. The outlet port of the valve casing is through a boss 7 36 secured by union 37 to a nipple 38 which is screwed into radiator A. A plate or disc 39 formed with an orifice 40 is arranged in the boss 36 and isheld against a shoulder 41 by a s lit ring 42. The orifice plate 39 is remova le so that the valve for each of the radiators of the heating system may be fitted with a plate having an orifice of the proper size to provide for the admission to the radiator of the proper amount of steam. The

orifices are of a size, when the system is filled -with steam, to admit enough steam to make up for condensation. That is the pressure in the radiators will equal the supply pipe pressure. The orifice plates function to dam back the steam onl when the system is started up. Thereby t ey insure the full supply of steam to the radiators remote from the generator.

In place of the radiator valve E with its orifice plate 39, a pressure reducing radiator valve may be used, suchas is shown in Fig. 9, which maybe connected to the radiator by same means as is shown in Fig. 2 for connecting the valve E; namely, a nipple. 38 screwed into the radiator and a union 37 connecting a boss 43 on the casing of the pressure reducing valve with nipple 38. o The casin r of the pressure reducing valve consists 0 upper and lower casing members 44, 45. Between these members is a flexible diaphragm 46. The lower casing member has an inlet port 47 in which is arranged a valve seat 48. A valve body 49 cooperates with seat 48 and is provided With a stem 50 secured to a button 51 to which diaphragm 46 is fastened. A flexible, corrugated structure '52 is secured at the top between the stem members 53, 54 and at the bottom against a web 55 of the upper casing member by means of a nut 56.- Stem member 53 is threaded for nut 57 and has a disc-like projection 58 adapted to bear, adjustably, upon a spring 59 which seats upon web 55 above referred to. Steam from the radiator supply pipe D can by-pass the valve seat 48 through a duct 60 so as to reach the under side of diaphragm 46. The chamber 61 above the diaphragm is connected to the interior of the radiator by a pipe 62. Stem member 53 projects into a bonnet 63 on the upper casing membpr 44. This bonnet is internally threaded to receive the threaded portion 64 at the end of an operating stem 65 which is provided with a hand grip 66 which can be utilized, however, only for closing the valve. The valve body 49 may be seated on the valve seat 48 by turning the hand grip 66 but when the valve is not seated in this positiye way its position with respect to the valve seat will depend upon the diiference of steam pressures on opposite sides of diaphragm 46 and upon the pressure of spring 59 which may be varied by adjustment of nut 57. When the pressure builds up in the radiator to a certain point diaphragm 46 will be deflected downwardly so as to close or throttle the steam inlet to the radiator. When the pressure falls in the radiator the diaphragm will be raised so as to increase the effective size of the inlet port. When this device is used radiator pressure may be less than supplypipe pressure, but will be dependent thereon;

The thermostatic trap F may be of 'any preferred construction provided it is capable of functioning effectively over the range of pressures which the system handles. It functions when steam is in contact with it to close the outlet of the radiator, opening,

the radiator free from water and allowing the outflow of air when the system is started T he trap I may be of similar construction and is arranged so that air may be Vented from the drip pipe 11 through return main G, the trap preventing the flow of steam from one of these pipes to the other. As traps of this sort arc in-common use, detailed description of the same will not be required.

Air eliminator J (Fig. 7). 67 is a casing connected to pipes 4 and 5 above referred to and containing a float 68. On the upper end of float 68 is a valve 69 which extends through a perforated baffle plate 70 secured between the upper flange 71 of casing 67 and a cover plate 72. Preferably a downwardly curved baflle plate 7 3 is secured to the plate 70. Valve 69 is adapted to seat, when the float is raised, on a valve seat 73 74 is an air exit pipe provided with the outwardly opening check valve 6 referred to above. The float 68 is provided at the bottom'with a guide pin 75 extending into an orifice in a bridge 76 across the outlet opening 77 of casing 67.

Exhausting apparatus. The hurling water chamber L and the casing of the air separator O are preferably formed of a single casting as shown in Fig. 4. Water enters chamber- L from the drip pipe H through pipe 11 and leaves the chamber L through a port 78 (Fig. 3). The casing of centrifugal pump M consists of a web 79 depending from tank L and a plate or casing member 80 secured to the web and to the front wall 81 of the tank by screws 82. Plate 80 is formed so as to provide a duct 83 extending from port 78 to the center of plate 80 in line with the shaft 84 of the pump. The latter is coupled at 85 to the armature shaft 86 of motor P and is supported in a bearing 87 carried by a bracket 88 on the under side of tank L and by a bearing 90 in a boss 91 on the rear face of web 79. The impeller of the pump is keyed to shaft 84 at 92 and consists of a pair of discs 93, 94 connected by curved blades 95. Disc 94 is formed with an opening 96. The discharge space 97 of the pump casing communicates with an outlet duct 98.

From duct 98 the water is forced through the jet exhauster shown in Fig. 6. This device consists of a casing 99 formed with a vacuum space 100 connected with the return main G by means of pipe 10; the casing being secured by nipple 101 and union 101 to the end of duct 98 and being formed with a bore 102 tapered from top to bottom. A discharge nozzle 103 is fitted into an enlargement 104 of bore 102 and extends across the vacuum space 100 into proximity with the end of a receiving nozzle 105 screwed into the top of casing 99 and formed with a straight bore 106, and beyond this, with a flared bore 107, the upper end of member 105 being connected with a conduit 108 which extends to an opening 109 in the side of the air separator O. The purpose of tapering bore 102 is to nullify the effect of the possible warmth of the water in the hurling circuit by utilizing the expan sion of the stream in bore 102 to increase the kinetic energy of the jet from nozzle 103.

The float 15 is carried on a lever 110 pivoted to a clevis 111 and provided with a depending arm 112 to which is pivoted valve 16, the latter being arranged to cooperate with a valve seat 113 fixed in the front wall 114 of the air separator. Valve 14 is arranged-on the end of a rod 115 pivoted to lever 110 and cooperates with a seat formed on an air venting member 116, the bore of which has been designated 13. Check valve 18 is. pivoted in a vent member 117 on the outside of the front wall 114 of the air separator. The bearing 90 of the pump shaft 84 is preferably lubricated by water taken from the discharge space 97 of the pump casing through a pipe 118.

The operation of the pump is intermittent, the pump being designed to maintain a determinate, but variable, pressure differential as between the boiler and supply pipe side of the radiators.

Q, is a circuit breaker, of any desired type,

operated by the pressure actuated device R shown in Figs. 4 and 8. This device consists of an upper casing member 119, a lower casing member 120, a flexible diaphragm 121, the edge of which is clamped between the flanges of said casing members, a rod 122 secured to the diaphragm, and a coiled spring 123 interposed between the upper casing member and the diaphragm. Rod 122 extends through a stufling box 124 and is pivoted to a lever 125 fulcrumed at 126 to the bracket 126 which supports the switch Q. A link 127 connects lever 125 with the operating arm 128 of switch Q. The chamber 129 below the diaphragm 121 is connected by pipe 20 to some point in the system under boiler pressure. For example, it may be tapped into the side of duct 98. The chamber 130 above the diaphragm is connected to the low pressur side of the system, for example, by pipe 19 extending to pipe 10. The differential controller is shown with its diaphragm in the position it will occupy when the pump is operating. If the pressure in the return main is diminished, relative to boiler pressure, through operation of the exhausting mechanism, or if the boiler pressure increases, relative to the pressure in the return main so that the determinate difference in pressure exists for which the controller is set to act, the diaphragm will be raised raising rod 122 and throwing switch arm 128 to break the circuit through the pump motor Pf. For the purpose of adjusting the dififerential controller, link 127 is made in two parts which are slotted and secured together by set screws 131.

Summary of 0peratz'on. Figs. 1 to 9 inclusive.) Any one of severa different operating conditions may prevail in the system as follows:

First. Operation in sta'rting.--The thermostatic'traps F of the radiators will be open. Assuming that the current is available to supply the pump motor, the pump will be started since there will be substantially no diil'erence in pnessure between the boiler and the return main G. The circulation of the water through the hurling circuit will produce a pressure below atmosphere in the vacuum chamber 100 of the jet exhauster and throughout the entire system since the radiators, supply main B and the steam space of the boiler will be in communication with the return main through the open thermostatic traps F. As a result the evaporation of the water will be commenced at a lower temperature than if the boiler were under atmospheric pressure. That is to say, thcapparatus will start to supply steam to the radiators, though at a lower temperature, than if the boiler were subject to atmospheric pressure. Moreover, the steam delivered by the boiler will be evenly distributed throughout all of the radiators of the heating system. The exhausting apparatus effects the withdrawal of air and water of condensation from the radiators but the air and entrained moisture only are drawn into the hurling circuit. The water of condensation collects in the vertical leg 24 of the return main G and when the column of water in pipe 24 stands above the level a, a of the water in the boiler to an extent sufiicient tov overbalance the boiler pressure, the condensate will enter the boiler by gravity. Any excess of condensation in the drip pipe will return to the boiler by gravity and since the drip pipe is under boiler pressure the water in pipe H will stand at the level of the water in the boiler, that is, a height just a trifle above pipe 11 and at about the'level of the upper portion of the hurling circuit L so that the pump will always be prim-ed. The hurling water from the jet exhauster, mixed with the air drawn from the return main, is discharged into the air separator O. The air escapes to the atmosphere through vent port 13, The water is trapped in the separator chamber by valve 16 until a sufficient amountaccumulates to raise float 15, whereupon valve 14 is moved to close the air vent and valve 16 unseated. As soon as the accumulation of air pressure in the separator 0 plus the static head of water therein overbalances boiler pressure in tank L the water from the air separator passes through duct 17 into the hurling water tank L. The hurling water circuit is. however, continuously supplied with water from the drip pipe through pipe 11 so that no interruption or impairment of the exhausting jet results through the interruption of the discharge of water from tank 0- to tank L. A sufiicient supply of water to the pump through pipe 11 is insured since the drip pipe H is under boiler pressure and by the fact that pipe 11 is slightly below the water level of the boiler. The function of pipe 3 with its steam trap I is, first, to vent any air in the drip pipe to than that at which the differential controller R is set to function.

Second. Normal operatiom-Jt will be now assumed that the radiators have become filled with steam so as to bring about the closing of the radiator traps F, these traps I opening onlyto allow the escape from the radiators of air and water of condensation. The system is now operating under normal conditions and, preferably, the differential controller will be adjusted to maintain a difference in pressure as between the supply ipe and the return main which is slightly ess than the hydrostatic head of a column of water of a height equal to the distance between the water. level of the boiler and the horizontal leg.23 of the return main. That is, the intention is to maintain a difference in pressure between the supply and the return sides of the system which will permit the condensate in the return main to enter the boiler by gravity. Several advantages result from the arrangement whereby the condensate, instead of being forced back into the boiler by the hurling water pump, enters the boiler by gravity or otherwise independently of the hurling water pump. The pump and its motor may be madesmaller and consumption of current diminished. The pump will be under boiler pressure on its induction side but not on its eduction side, ex,- cept for short periods so that whatever pressureexists in the boiler is utilized to aid the pump in developing the exhausting jet. The exhausting apparatus and the hurlingwater chambers may be reduced in size.

Under the operating conditions last specified, the system will operate either above or below atmospheric pressure in accordance with the changing ratio as between steam supply and condensation. In either case, a constant difi'erence of pressure is maintained between the supply piping and the return main which insures a proper circulation of the steam throughout the system and the filltemperatures the radiating system will be at pressures below atmosphere. The radiatingsystem will'be at atmospheric pressure condensation, and this pressure differential reaches the point at which the controller R is set to act, the pump will be stopped until, through leakage of air into or accumulation of condensate in the return main, or reduction in the rate of steam supply, the pressure differential is reduced to a point which sets the pump again in operation. The action of the pump is, therefore, intermittent.

' It maintains, effectively, a constant diflerence in pressure between the supply and return sides of the system. Condensate in the return main can at, all times, under the conditions assumed, flow back to. the boiler by gravity since the pressure in the boiler will not be in excess of the static head of water in pipe 24.

The temperature of the steam in the radiators depends upon the amount of steam per unit of time admitted to the radiators. This,

in the present embodiment of the invention, is adjusted by controlling the generation of steam through thermostatic control of the dampers of the generator.

When the system is operating sothat the pump tends to produce subatmospheric pressures in the return main and throughout the system, check valves 6 of air trap and elim inator J and 18 of air separator 0 will be closed to permit the maintenance of the low pressure.

At any time in the operation of'the apparatus when the boiler pressure is greater than will be balanced by a column of water equal in height to the distance between pipe 11 and the top of air separator O, theseparating chamber will be filled with water reaching the chamber throughthe pump and jet exhauster. In such case the water is prevented from entering-the return main by check valve 12. The water in the separating chamber will be prevented from flowing to the atmosphere because of the closing of air outlet duct 13 under action of fioat 15. Now, if the pump starts as a result of diminished pressure differential, the jet exhauster will draw air from the return main into the air separator so as to create an air pressure above the water in the separator. This body of compressed air will lower the water level 1n the air separator, causing the water to flow into the hurling water tank L, and if the return main G (whether the system is at sub-atmospheric pressures or at pressures slightly above atmosphere) which is slightly less than the pressure exerted by the hydrostatic head of a water column equal in height tothe distance between the water level of the boiler and the horizontal leg 23 'of the returnmain. To avoid circumlocution this differential will be referred to as the normal differential as between the supply pipe and return main. Where the system is provided with a thermostat K for controlling the dampers of the steam gen er-ator, this thermostat may be set so that steam will be generated at a rate just rapid enough to equal the heat lost from the build Y ing. For average temperatures the steam generated will be insuflicient to fill the radiators at atmospheric pressure and therefore expands so that the pressure in the radiators is less than atmosphere. The pressure differential may be no more than necessary to move the medium through the radiating system. However, the system is intended to operate, when circumstances require it, with a pressure difference above the normal differential, as mentioned above; and this phase of the operation of the system will now be described.

Third. Operation with pressure dz'flerenee above n01maZ.Whenever the pressure difference isabove normal, as just defined, as will be the case when the rate of heat loss is abnormally high, the pump will be out of operation s'ince'difierential controller R'will have functioned to break the circuit through the pump motor. The pump will remain out of operation until the pressure difference has been reduced to a point below normal. Under these conditions water will accumulate in the vertical leg 24 of the return main filling the same up to the top and also filling the air trap and eliminator J, the float 68 of which is caused to rise so as to seat valve 69 to close the vent pipe 74 (Fig. 7). j The continued'flow of water of condensation and gaseous fluids from the radiators, by gravity and the pressure difference between the supply and return sides of the system, will create a pressure in pipe 23 of the return main and in the air trap and eliminator J above the water line therein, until the pressure in the return main plus the pressure of the water column in p1pe 24 overbalances boiler pressure whereupon water from the return main will flow into the boiler by gravity. If the pressure difference is reduced to the point where the difierential controller R acts, the pump will be started.

Fourth. Operation with declining fire and the pump -operatiue. In case the fire declines so as to supply insufiicient steam to fill the radiators, the systemwill function substantially as when the apparatus is first started up, that is, as has been described in paragraph first. The exhausting apparatus will be in operation since the pressure differential is below normal. But with insufiicient steam in the radiators thermostatic traps F will open sothat the reduced pressure created by the exhausting apparatus will extend to the radiating system and the steam space of the boiler. tion temperature of the boiler water, increasing the amount of evaporation so as to increase the supply of steam to the radiators Thus the radiators will be automatically filled with steam but at a lower temperature.

Fifth. Operation with the pwmp out of action and the boiler at or below a pressure corresponding to the static head of the return main.It is one of the advantages of my invention that the system will operate even if the pump through failure of current to the motor, for example, should cease to act. Under these circumstances, and with the boiler pressure less than the hydrostatic head of a water column of a height equal to the distance between the water level in the boiler and the horizontal leg 23 of return main G, water of condensation in the return main will flow by gravity into the boiler. With the apparatus operating in this manner one does not have they advantages resulting from the maintenance of a constant pressure differential as between supply piping and return main and the economies which follow from operation at sub-atmospheric pressures during average weather conditions but the system will, nevertheless, operate successfully. This is because the return of condensate from the radiators to the boiler is brought about by gravity and is independent of the functioning of the pump.

Sixth. Operation with the pump out of aetion and the boiler at a pressure greater than that corresponding to the static head of thereturn main.-Under these conditions the accumulation of condensate in the return main will flood the air trap and eliminator J causing its float to'close the vent pipe 74. The

continued flow of condensate from the radia-' This will diminish the evapora-- pressure permits the static head of water in the return main toforce condensate into the the pump in operation. The air present in the system at the time the fire starts to decline and that subsequently entering by leakage will necessarily ex and as the decrease in pressure proceeds an as the pump is not in operation no. means is available for decreasing the amount of this air.

In Fig. 10 a system is shown operating u on the general principles above described, utmodified so as to include a return trap for introducing condensate from the dry return main into the boiler. In Fig. 10 the elements of the heating system common to the modification there shown and the form of the invention illustrated'in the previous figures are given thereference letters and numerals heretofore used. In the modified form of the apparatus the horizontal leg 132 of. the return main G extends to a return trap T. The vertical leg 133 of the return main is connected to the bottom of trap T. The return trap is of a type'in common use. Water collects in the trap, the bottom of which is in free communication with the pipe leading to the boiler. The trap has an air vent plp'e' 134 and a pipe 135 connecting it with the boiler. The openings between the traps and these pipes are provided with valves under control of a pivoted float 136. When the float is down vent pipe 134 is open and steam pipe 135 closed. When enough water has accumulated in the trap'to raise the float, the valve controlling the air vent pipe is closed and the valve controlling the steam pipe opened so that a steam pressure is exerted on the water in the trap balancing boiler pressure and the water flows by gravity into the boiler. 'In the drawings I have shown a return trap which is the subject matter of the patent of Oscar G. Johnson, 1,509,299, granted September 23, 1924. Any other trap of this general type might be used in place of that shown. H v

In connecting up the return trap with the heating system of my present invention a check valve 137' is arranged in pipe 132, the valve opening in the direction of the trap, and

the air eliminator J is connected with a T 1 138 on the vent pipe 134 by an equalizing pipe 139 provided with a check valve 140 which opens toward the air eliminator. Projecting from the other side of the'T 138 is a pipe 141 open to'the atmosphere and provided with an outwardly opening check valve 142.

. tem.

Operation of the system with return trap. (Fig. 10.) lVhen the heating apparatus is is .lirst started up the operation will be the same as in the gravity-return system of Fig. 1. That is,the thermostatic traps of the radiators will be open and the entire system will operate at sub-atmospheric pressure, with the result that steam will be delivered to the radiators more quickly than if the boiler were un der atmospheric pressure and the distribution of steam will be uniform throughout the sys- Condcnsation collecting in the return main will flow by gravity through the trap T and into the boiler under the hydrostatic pressure of the water in the pipe 133 and in the trap. The vacuum is maintained by check valves 6 and 142. The horizontal pipe 132 of the return main G is formed, preferably, with a downward bend 143 to overcome the resistance of check valve 137.

So long as the pressure ditferentialas between the supply piping and the return main is at or less than normal, that is, represents a 5 established and is automatically stopped by the differential regulator when the normal differential is exceeded.

If, however, due to excess of steam generated over condensation, the normal differential is exceeded, and this condition persists, the trap will function to return the water of condensation to the boiler as follows: Under this condition water will collect in the trap T since the Water column in the trap will be insufficient to balance the assumed boiler pressure. This causes the float 136 of the trap to rise, closing the vent pipe 134 and opening the trap to the steam pipe 135. Steam enters the trap at boiler pressure and the water in the trap flows by gravity to the boiler.

- Check valve 137 shuts olf the high pressure in the trap from the return main. The condensate collecting in the return main is prevented from escaping through the air vent of eliminator J by the float controlled valve of said the pressure difl'erential above normal, the

system having a return trap as shown in Fig. 10 hasa certain advantage over the system shown in Fig. 1, in that steam pressure from the boiler is employed for returning condensation to the boiler instead of a pressure developed by the pump. That is to say, electric current consumption is economized.

With a declining fire the system of Fig.

operates exactly the same as the system of 1g. 1. I

With the pump out of action, through failure of current, for example, the system of Fig.

10 operates exactly the same as the system of Fig. 1, provided the boiler pressure does not exceed atmospheric pressure prevailing in the return main by an amount in excess of What has been termed the normal pressure diflerential. That is, with the pump out of action water of condensation will flow by gravity back to the boiler so long as the boiler pressure is such that it can be overbalanced by the head of water collecting in trap T and pipe 143. v

If the boiler pressure exceeds this pressure the trap will-operate to return the water of condensation intermittently to the boiler as device comprises three dished or recessed plates 144, 145, 146 between which are arranged flexible diaphragms 147, 148. Pipe 21 connected with the low pressure side of the heating system leads to the chamber 149 between diaphragm 148 and plate 146. Pipe 22 connected with the high pressure side of the heating system leads to chamber 150 between plate 144 and diaphragm 147-. Chamber 151 between diaphragm 147 and plate 145 is connected by a duct 152 and elbow pipe 153 with one leg 154 of a U-shaped gauge glass 155 supported by a bracket 156 depend ing from plate 146. The other leg 157 of the gauge glass is connected by an elbow 158 and a duct corresponding to duct 152 with the chamber 159 between diaphragm 148 and plate 145. The gauge glass contains a body of mercury 160 and chambers 151, 159, together with the pipe connections 153, 158, and the legs of the gauge glass above the mercury are filled with water. 161 is a gauge plate having graduations upwardly on the vacuum side and downwardly on the pressure side from a common zero line coinciding with the tops of the mercury columns in the gauge glass when said columns are balanced, that is, when the pressures in the supply U piping andreturn main are equal. Any difference of pressure as between thesupply piping and return main will be indicated by the rise of one mercury column and the fallin of the other.

Vhile I have described my invention in certain preferred embodiments, I wish it to be understood that I contemplate all further modifications within the scope of the appended claims.

While the invention is shown and described as embodied in a heating system for a single building having its own steam generator, the novel constructions and arrangements constituting the invention might be'utilized in connection with a central station system in which several buildings are heated from a single central boiler plant.

I do not claim specifically herein the form of apparatus shown in Fig. 10 as such apparatus is the subject of a divisional application, filed Dec. 31, 1927, Serial No. 243,861. Nor do I claim herein the invention common to this application and my previous application Serial No. 669,363, filed October 18, 1923, as such generic invention is claimed in the earlier filed application. By the term heating medium as used in the claims I 1ntend to include the fluids circulated through the radiating system, to wit, the steam, vapor, water of condensation and entrained air or other non-condensible gases.

I claim:

1. Steam heating apparatus comprising in combination a steam generator, controlling devices for the generator, a radiating system, connections for supplying the radiating system with steam from the generator and withdrawing fluids therefrom comprising a supply conduit and a return conduit, means for maintaining selected pressures below atmosphere in said radiating system in accordance with the heat output desired and a predetermined diflerence of pressure between the supply and discharge conduits sufficient to move the steam through the system, and a thermostat connected with the controlling devices of the steam generator for limiting the quantity of steam generated to that required for supplying the radiating system. i

2. Steam heating apparatus comprising in combination a steam generator, controlling devices for the generator, a radiating system having an inlet and an outlet, connections for supplying the radiating system with steam from the generator, means for maintaining selected pressures below atmosphere in said radiating system in accordance with the heatoutput desired and a predetermined difference of pressure between its inlet and outlet sufficient to keep up movement of the steam through the system, and a ther'mostat subject to heat from the radiating system and connected with the controlling de- 3. In steam heating apparatus the combination of a steam generator, a radiating system comprising a plurality of radiators, a

supply pipe'leading from the generator and i a drip pipe leading from the supply pipe back to the generator, branch p1pesconnecting the supply pipe with the inlets of said radiators respectively, a return pipe connected with the generator, branch pipes leading from the outlets of the radiators to the return pipe, steam traps in said last named branch pipes, and means for maintaining selected pressures below atmospheric in said radiating system, comprising an exhausting mechanism withdrawing only non-condensible gases from the return pipe to maintain a predetermined difference of pressure between the supply and return pipes sufiicient to move the steam through the radiating system.

4. In steam heating apparatus the combination of a steam generator, a radiating system comprising a plurality of radiators, a supply pipe leading from the generator and a drip pipe leading from the supply pipe back to the generator, branch pipes connectcient to move the steam through the radiat-' ing system.

5. in steam heating apparatus the combination of a steam generator, a radiating system comprising a plurality of radiators, a

supply pipe leading from the generator and a drip pipe leading from the supply pipe back to the generator, branch pipes connecting the supply pipe with the inlets of said radiators respectively, a return pipe connected with the generator, extending above the Water level therein to provide a hydrostatic head for return of water against the pressure in the generator, branch pipesleading from the outlets of the radiators to the return pipe, steam traps in said last named branch pipes, and means for maintainingselected pressures below atmosphere in said radiators in accordance with the heat output desired and a predetermined diiference of pressure between the supply and return pipes I suflicient to move the steam through the midiating system, this means including exhausting apparatus connected with the return pipe so as to remove therefrom onlyair and gases.

6. In steam heating apparatus the combination of a steam generator, a radiating system comprisin a plurality of radiators, a sup- 1y pipe leading from the generator and a ri pipe leading from the supply pipe back to t e generator,.branch pipes connecting the supply pi e with the inlets of said radiators.

respective y, a return pipe connected with the hausting mechanism comprising a hurling water pump'under the pressure in the genera- .tor on its induction side only.-

9. In steam heating apparatus the combination of a steam e'nerator, a radiating sysgenerator, branch pipes leading from the tem comprisingap urality of radiators, a supoutlets of the radiators to the return pipe, steam traps in said last named branch pipes, and means'comprising exhausting mechamsm connected with the return pipe so as to remove therefrom only non-condensible gases, said means maintaining selected pressures'below atmosphere in said radiators in accordance with the heat output desiredand a predetermined diflerence of pressure between the supply and return pipes-suflicient to move the steam through the radiating system, an exhaust pipe between the drip pipe and the return pipe and a steam trap in said last named 1 p In steam heating apparatus the combination of a steam generator, a radiating system comprising a plurality of radiators, a supply pipe leading from the generator and a drip pipe leading from the supply pipe back to the generator, branch pipes connecting the supply pipe with the inlets of said radiators respectively, a return pipe connected with the generator, branch pipes leading from the outlets of the radiators to thereturn pipe, steam traps insaid last named branch pipes,

and means comprising exhausting mechanism connected with the return pipe so as to remove therefrom only non-condensible gases, said means maintaining selected pressures below atmosphere in said radiators in accordance with the heat output desired and a predeter-.

mined diiference of pressure between the supply and return pipes sufficient to move the steam through the radiating system, said exhausting mechanism comprising a hurling water pump positioned below the water level of and connected with the generator so as to receive its hurling water therefrom and discharge excess water thereto.

8. In steam heating apparatus the combination of a steam generator, a radiating system comprising a plurality of radiators, a supply pipe leading from the generator and a dri pipe leading from the supply pipe back to t e generator, branch pipes connecting the supply pipe with the inlets of said radiators respectively, a return pipe connected with the generator, branch pipes leading from the outlets of the radiators to the return pipe, steam traps in said last named branch pipes, and means comprising exhausting mechanism connected with the return pipe so as to remove ply pipe eading fromthegenerator "and a drip pipe leadin from the supply pipe back to the generator, branch pipes connectin the supply pipe with the inlets of said ra iators respectively, a return pipe connected with the generator, extending above the water level therein to provide a hydrostatic head for return of water against the pressure in the generator, branch pipes leadmg from the radiators to the return pipe, steam traps in said last named branch pipes,- and means comprising an exhausting mechanism connected with the return pi so as to remove therefrom only non-condensile gases, said means maintaining selected pressures below atmosphere in said radiators in accordance with the heat output desired and a predetermined difference of pressure between the supply and return pipes suflicient to move the steam through the ra turn pipe which opens toward the generator.

10. In steam heating apparatus the combination of a steam generator, a radiating system comprlsing a plurality of radiators, a suppl pipe leadin from the generator and a rip pipe lea 'ng from the supply pipe back to the generator, branch pipes connecting the supply pipe with the inlets of said radiators respectively, a return pipe connected with the generator, branch plpes leading from the outlets of the radiators to the return pipe, steam traps in said last named branch pipes, exhausting means connected with the return pi e so as to remove therefrom only non-con ensible gases for maintaining a predetermined difference of pressure between the supply and return pipes suiiicient to move the steam through the radiat ng system, and means cooperating with said exhaustlng means for controlling the amount of steam admitted into the radiating system so. as to vary the temperature of the steam in theradiators in accordance with the heat output desired.

11. In steam heating apparatus the combination of a steam generator, a radiating system comprislng a plurality of radiators, a supply p1pe leading from the generator and a drip pipe leading from the supply pipe back to the generator, branch pipes connectmg the supply pipe with the inlets of said radiators respectively, a return pipe conradiators in accordance I ,diating system, and a check valve in the renected with the generator, branch pipes leading from the outlets of the radiators to the return pipe, steam traps in said last named branch pipes, and heat control means comprising an exhausting means connected with the return pipe so as to remove therefrom only non-condensible gases said heat control means maintaining selected pressures below atmosphere in said radiators and a predetermined difference of pressure between the supply and return pipes suificient to move the steam through the radiating system, said exhausting means comprising a hurling water circuit and ump and means for elimi nating non-con ensible gases from the hurling circuit.

12. In steam heating apparatus the combination of a steam generator, a radiating system comprising a plurality of radiators, a suppl pipe leading from the generator and a rip pipe leading from the supply pipe back to said generator, branch pipes connecting the supply pipe with the inlets of said radiators respectively, a return pipe connected with the generator and extending above the water level therein to provide a hydrostatic head for return of water against the pressure in the generator, branch pipes leading from the outlets of the radiators to the return pipe, steam traps in said last named branch pipes, heat control means comprisin an exhausting mechanism connected with t e return pipe so as to remove therefrom only non-condensible gases, said heat control means maintaining a pressure below atmosphere in said radiators and a predetermined difference of pressure between the supply and return pipes sufiicient to move the steam through said radiating system, said exhausting mechanism comprising a hurling water circuit arranged below the water level of and connected with the generator to receive its hurling water therefrom and to discharge excess water thereto, a pipe between the supply and drip pipe and the return pipe, a steam tra in said last named pipe, a check valve in t e return pipe which opens toward the generator and a float controlled air trap and eliminator connected with the return pipe-and comprising an outwardly o ening check valve.

13. In steam eating apparatus the combination of a steam generator, a radiating system comprising a plurality of radiators,

supply and return pipes connecting the radiat-ing system with the generator for supply of'steam to the radiating system and return of condensation to the generator, steam traps between the radiators and return pipes, exhausting means which withdraws only noncondensible gases, from the return piping for maintaining a predetermined diflerence of pressure between the supply and return pipes suflicient to move the steam through the radiating system, and means cooperating with the exhausting means for controlling the amount of steam supplied to the radiating system to vary the temperature of the steam in the radiators in accordance with the heat output desired.

14. In steam heating apparatus the combination of a steam generator, a radiating system comprisinga plurality of radiators, supply and return pipes connecting the radiating'system with the generator for supply of steam to the radiating system and return of condensation to the generator, steam traps between the radiators and return pipes, through which both water and non-condensible gases pass to the return pipes, and heatcontrol means including an exhausting mechanism which withdraws only non-condensible gases from the return pipes, said heat control means maintaining selected pressures below atmosphere in the radiators and a predetermined difl'erence of pressure between the supply and return pipes suflicient to move the steam through the radiating system, said heat control means also including restricting devices at the inlets of the radiators for limiting the inflow thereto of steam .to the maximum radiating capacity of said radiators respectively.

l5. In steam heating apparatus the combination of a steam generator, a radiating system comprising a plurality of radiators, supply and return pipes connecting the radiating system with the generator for supply of steam to the radiating system and return of condensation to the generator, steam traps between the radiators and return pipes through :which both water and non-condensible gases pass to the return pipes, heat control means comprising exhausting mechanism for withdrawing only non-condensible gases from the return pipes to maintain selected pressures below atmosphere in the radiators and a predetermined difference of pressure between the supply and return pipes suflicient to move the steam through the radiating system, and orifice plates in the inlets of the radiators for restricting the inflow of steam to the radi- CLAYTON A. DUNHAM. 

